Optical fibers are waveguides with a well-defined axis of propagation that typically include a core and a cladding that surrounds the core. The core material has a higher refractive index than the cladding material, and the optical fiber guides radiation along a waveguide axis by confining the radiation within the core due to total internal reflection of the radiation at the core-cladding interface. Fiber lasers are typically composed of optical fibers in which the core is doped with a gain medium. A pair of reflectors (e.g., mirrors or fiber Bragg gratings) positioned at opposing ends of a length of doped fiber defines an optical cavity in which optical feedback can occur. During operation, the gain medium is pumped, e.g., by pump radiation directed into the core. Radiation emission from the pumped gain medium is amplified through feedback within the optical cavity, while being guided back and forth between the reflectors and confined to the core. Generally, some of this radiation is transmitted by at least one of the reflectors and exits the fiber at an end of the fiber.